While the primary function of a storage system is to provide power when sunlight is not available, hence increasing the fraction of time the photovoltaic system provides electricity, the addition of batteries has numerous other advantages which mean that the batteries can be used for multiple purposes. For small systems consisting of one or two photovoltaic modules, batteries can act as a load-matching system. Alternately, in photovoltaic systems which contain a load with a large initial current draw (such as experienced by an inductive load, typically represented by a motor), the batteries can be used to provide initial start-up current. In grid-connected systems, battery storage can be used for peak shifting, in which the power generated by the sun is stored for several hours in order to better match when the peak load occurs.

In various useful units, the universal gas constant can be written

R = 8.3144 x 10⁷ erg mol^-1 K^-1
   = 8.3144 J mol^-1 K^-1
   = 8.2057 x 10^-2 l atm mol^-1 K^-1
   = 1.9872 cal mol^-1 K^-1
   = 62.363 l torr cal mol^-1 K^-1

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